Imbalance compensation element, pump, and method for balancing pumps driven by an electric motor

ABSTRACT

The present invention describes an imbalance compensation element featuring spring arms for fixing onto a shaft, and that grooves in which an anaerobic adhesive can distribute itself for fixing the imbalance compensation element on a motor shaft. One embodiment includes a pump with such an imbalance compensation element. In a method for balancing such electric pumps, the axial and radial oscillation accelerations as well as the oscillation angular position of a running pump are measured. In accordance with these measurements and the balance class and balance angle values ascertained therefrom, an imbalance compensation element is fixed on the shaft. Through this invention the time and cost required for balancing pumps driven by electric motors can be reduced and the acoustic emissions can be distinctly reduced when such a pump is installed on a housing.

This application claims priority on DE 10 2004 044 070.0 filed Sep. 11, 2004, the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the invention

The invention relates to an imbalance compensation element for fixing on one end of a motor- or pump shaft, whereby the imbalance compensation element features an inner circumferential surface coaxial to the central axis whose inside diameter corresponds essentially to the outside diameter of the shaft, as well as a pump, in particular an air injection reactor pump for combustion engines, which pump is driven by an electric motor, whereby at least one impeller of the pump is arranged on a drive shaft of the electric motor, as well as a method for balancing such a pump driven by an electric motor.

2. Background Art

Certain imbalance compensation elements, pumps, and methods for balancing in such pumps by means of imbalance compensation elements are known and are described in a number of Applications. Thus in DE 93 03 470 U1 a fan is described whose impeller is arranged on a shaft driven by an electric motor, whereby a balancing weight is placed on the end of the shaft projecting from a housing aperture in order to balance the fan. The imbalance compensation element used thereby is a radially divided ring that can be embodied in different widths and weights. In a described form of embodiment, the imbalance compensation element is formed by a Seeger circlip ring, which after the final testing of the fan is inserted into a circular groove of the shaft by means of Seeger circlip ring pliers and is oriented according to the determined imbalance.

From EP 0 711 924 B1 an electrically driven air pump is known that features a housing in which both an electric motor and the pump assembly are arranged, whereby a balancing of the electric motor with a mounted pump wheel in the installed state is carried out by placing balance marks on an impeller of the pump wheel before the pump side is closed.

As a rule the known methods are iterative methods in which the measured imbalance is to be minimized at each further step by repeatedly allowing the electric motor or the pump to run. This can be carried out for example by means of small holes in the impellers. Thus these are nonclassified imbalance compensation elements.

SUMMARY OF THE INVENTION

The object of the invention is to create a classified imbalance compensation element that can be mounted on a pump shaft in a single operation, for which purpose if possible only a single measurement of the imbalance should be required. The transmission of acoustic emissions, in particular structure-borne noise, after installation for example on a combustion engine or a body of a vehicle is to be minimized.

This object is achieved in that the inner circumferential surface of the imbalance compensation element features flexible spring arms in a first section, which spring arms are embodied such that in the installed state, the spring arms produce a frictional connection to the shaft at least in the circumferential direction. By these means it is possible to place the imbalance compensation element with positive engagement on one end of a motor shaft or on a hub of a pump at a measured balance angle. In spite of the unequal weight of the body, an unintentional twisting is precluded.

In a preferred form of embodiment the spring arms are embodied as ring segments extending in the axial direction, so that as a result the component can be produced cost-effectively and its shape is simple.

In a further embodiment of the invention the inner circumferential surface features grooves in a second rigid section that run in the axial direction, so that the positive engagement connection forces are also greater in this rigid section due to the smaller mounting surface and when fixed by means of adhesive, sufficient adhesive can be deposited in the grooves to create a firm, cohesive connection between the shaft or hub of the pump and the imbalance compensation element.

In a further form of embodiment of the invention the imbalance compensation element features a closed outer circumferential surface wherein over one or more first defined angular areas the closed outer circumferential surface is connected to said inner circumferential surface with a connection that is essentially completely filled with material, and wherein in one or more second defined angular areas, the closed outer circumferential surface is connected to the inner circumferential surface by one or more individual bridges. In this manner a counterweight to the imbalance present is created, since the center of gravity in the axial direction of this imbalance compensation element does not lie in the center. Moreover the embodiment with the individual bridges between the circumferential surfaces still guarantees adequate strength in the otherwise hollow area.

In a preferred form of embodiment the imbalance compensation element is produced as one piece using the injection molding process, by means of which time and production costs are minimized.

Moreover the above-described object is achieved by a pump in which the drive shaft projects beyond the impeller of the pump in the direction facing away from the electric motor so that an imbalance compensation element according to the invention can be fixed on the projecting end of the shaft. Thus no further changes need to be undertaken to existing components of the pump such as the impellers for imbalance compensation. The arrangement of such an imbalance compensation element on the shaft end is to be carried out in one operation.

In a preferred form of embodiment a connection piece of the pump runs coaxially to the drive shaft so that in the completely assembled state, the pump can be tested and balanced.

In a further form of embodiment the imbalance compensation element is fixed on the drive shaft by means of an anaerobic adhesive with which the impellers can also be fixed on the drive shaft. Such an adhesive dries only when air has been excluded, so that an intermediate bearing of the pumps before the balancing is possible and the residual amount of adhesive on the shaft from the fixing of the impellers is sufficient to fix the imbalance compensation element.

In a further form of embodiment of the pump, the axial outer surfaces of the imbalance compensation element and of a hub of the pump impeller facing one another correspond in their shape, so that a clearly defined stop of the imbalance compensation element on the hub of the pump impeller is present and an exclusion of air is ensured.

The above-mentioned object is furthermore achieved by a method for balancing electric pumps of the invention by single-level balancing with the following steps:

-   -   (a) providing a pump connected to an electric motor;     -   (b) starting the electric motor;     -   (c) measuring an oscillation acceleration to determine         acceleration amplitudes in the axial and/or radial directions         together with measuring an oscillation angular position to         determine a balance angle and a balance class; and     -   (d) placing a classified imbalance compensation element         according in accordance with the determined balance angle and         balance class.

With such a method a single measurement suffices to compensate for the imbalance present.

To measure the oscillation angular position, it is preferable to use a light barrier as well as a reflecting disk connected to the drive shaft with positive engagement, which is simple to dismantle again after the measurement has taken place.

To measure the oscillation acceleration, it is preferable to use a triax sensor with which both the axial and the radial oscillation acceleration is measured at the pump.

It is preferable to carry out the measurements at the operating speed of the fully assembled pump, so that the imbalances actually occurring during the operation of the pump are also identified.

To further improve the results, the measurement of the oscillation acceleration is carried out at the mounts of the pump to the combustion engine or to the vehicle. After the pump is installed, this leads to distinctly reduced transmission of structure-borne noise to the engine housing or to the body.

If the oscillation angular position of the axial and radial acceleration amplitudes are not equal, the balance angle and the balance class are preferably calculated by weighting the acceleration amplitudes taking into consideration the oscillation angles. Through such a procedure, as a rule a balance process remains sufficient to achieve good results.

In a further operational step, the classified imbalance compensation element is fixed in a recess of an angular degree disk before being fixed on the shaft, so that after the balance angle to the zero position has been ascertained, the imbalance compensation element can be turned into the correct position to the shaft by turning the angular degree disk to the ascertained balance angle, can be pushed onto the shaft, and fixed. This leads to an exact fixing of the imbalance compensation element in accordance with the measured data. The number of measurements needed and assembly steps is reduced by such a method in comparison with other known methods.

Thus an imbalance compensation element is created that is simple to produce and mount and through which a high-quality balancing is produced with a single measurement. Accordingly a low-oscillation running of a pump equipped with such a balance element is ensured. The method for balancing such a pump with an imbalance compensation element according to the invention contains a distinctly reduced number of assembly steps in comparison with known methods. Thus a largely oscillation-free pump can be produced and assembled with a reduction in cost and time. After installation in the engine, acoustic emissions are reduced.

An imbalance compensation element according to the invention and a pump equipped with such an imbalance compensation element are shown in the drawings, whereby the method according to the invention for balancing such pumps is also described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an imbalance compensation element according to the invention in cross-section in side view.

FIG. 2 shows the imbalance compensation element from FIG. 1 in perspective view.

FIG. 3 shows a cross-section representation of a pump according to the invention using an air injection reactor pump as an example, in side view.

DETAILED DESCRIPTION OF THE INVENTION

The imbalance compensation element 1 shown in FIGS. 1 and 2 comprises a body that features an aperture 2 running axially, which aperture is limited by an inner circumferential surface 3. This inner circumferential surface 3 is divided into a first section 4 formed by flexible spring arms 5, and a second section 6 in which the aperture 2 features grooves 7. This second section 6 is immediately adjacent to the first section 4. The flexible spring arms 5 are formed such that recesses 8 running axially are arranged in this first section 4 and the imbalance compensation element 1 features a second aperture 9 whose diameter is greater than the diameter of the aperture 2. This aperture 9 extends up to the start of the first section 4 and continues in the form of a groove and coaxially in the section lying outside the axis. Accordingly the flexible spring arms 5 remain between this larger diameter of the second aperture 9 and the smaller diameter of the aperture 2. It must also be pointed out that these flexible spring arms 5, which are essentially formed by small ring segments, are slightly bent towards the axis in comparison with the diameter of the aperture 2, so that a spring force is exerted by them on a shaft, not shown here, that features a corresponding outside diameter.

Axially outwards the imbalance compensation element 1 is limited by an outer circumferential surface 10, which likewise runs essentially coaxially to the axis. In order to be able to undertake an appropriate imbalance compensation, the cavity forming between the inner circumferential surface 3 and the outer circumferential surface 10 is filled with material over certain angular areas, so that a connection 11 running over this angular area between the inner circumferential surface 3 and the outer circumferential surface 10 is ensured. In another radial angular area a connection between the circumferential surfaces 3, 10 is produced only by bridges 12 in order to ensure a fixing of the imbalance cap, and thus to be able to embody the walls of the circumferential surfaces 13 as thin as possible.

Depending on the desired balance class, the angular area filled with material can be selected larger or smaller. Different classified imbalance compensation elements are correspondingly available. The fill level along the axis can also be changed if necessary.

Moreover it can be seen in particular from FIG. 3 that the imbalance compensation element 1 features an axially limiting outer surface 13 whose shape corresponds to a hub 14 of an impeller 15 of an air injection reactor pump 16. This air injection reactor pump 16 is driven by an electric motor 17, whereby two impellers 15, 18 are arranged directly behind one another axially on a shaft 19, which shaft is embodied simultaneously as pump- and motor shaft 19.

When such an air injection reactor pump is being balanced, an imbalance compensation element 1 classified according to the balance class ascertained is pushed on to the motor shaft 19 at the balance angle ascertained. For this purpose, one end 20 of the shaft 19 is embodied lengthened. In order to be able to attach such an imbalance compensation element 1 when the pump 16 is completely assembled, a connection piece 21 is arranged coaxially to the shaft axis, whereby the connection piece 21 is embodied on a cover 22 of the pump 16 and is axially accessible. During the assembly of the air injection reactor pump 16, this cover 22 is mounted on a housing 23 in which the electric motor 17 is also fixed with intermediate layers of elastomer rings 24. This housing 23 is again closed by a second cover 25 at the end facing away from the side of the pump.

In the present case this is an air injection reactor pump 16 that is embodied as a two-stage radial fan. Electrical contacts 26 to connect the motor 17 to an external power source are led out of the housing 23. In addition, mounts 27 are embodied on the housing 23, to which mounts the air injection reactor pump 16 can be fixed during installation in a combustion engine or on the body of a vehicle.

A balancing of such an electric air injection reactor pump 16 is performed by first inserting the air injection reactor pump 16 into a holding device with an intermediate layer of elastomer rings. In the area of the mounts 27 a triax sensor is arranged that records the axial and radial accelerations arising due to a possibly present imbalance. Since no imbalance compensation element 1 has yet been arranged on the shaft 19 at this point in time, a reflecting disk is arranged at this location that interacts with a light barrier that is part of the holding device, through which the oscillation angular position can be measured in a known manner during operation. The completely assembled pump, which is now situated in the holding device, receives the electrical connections and is started. The values measured at the operating speed of the pump are decisive for the results of the triax sensor or the light barrier to be evaluated. In accordance with these measured values, a balance class and a balance angle are calculated, whereupon a corresponding classified imbalance compensation element 1 is pushed onto the shaft 19. This is done by placing the imbalance compensation element 1 in a recess of an angular degree disk and fixing it there in a zero position. After the balance angle to the zero position has been ascertained, the imbalance compensation element can be turned to the correct angle to the motor shaft 19 by turning the angular degree disk and can be pushed onto the motor shaft. The impellers 15, 18 of these pumps 16 are customarily fixed by means of an anaerobic adhesive, so that additional fixing means for the imbalance compensation element 1 are not necessary, since the residual adhesive present on the shaft suffices to fix the imbalance compensation element 1, which has been pre-fixed by the spring arms 5, finally on the shaft 19. The adhesive amount remaining from the fixing of the impellers 15, 18 of the pump 16 can distribute itself uniformly in the grooves 7, without the entire amount of adhesive being pushed from the shaft 19 during the placing. This anaerobic adhesive can then cure in a short time due to the exclusion of air between the inner circumferential surface 3 of the imbalance compensation element 1 and the outer surface of a shaft 19.

If the oscillation angular position of the axial and the radial measured accelerations are not the same, the balance angle is calculated by weighting the acceleration amplitudes taking the respective oscillation angles into consideration.

Thus a distinctly reduced oscillation load of the air injection reactor pump can be achieved by means of a single measurement at operating speed of the pump and measurement of the accelerations at the actual mounts as well as measurement of the oscillation angles of the air injection reactor pump, as a result of which in particular acoustic emissions in the vehicle are reduced to a particularly great extent. The imbalance compensation element to be arranged on a pump for this purpose can be produced simply and cost-effectively and can be pre-fixed by the spring arms. A great reduction in cost and time with a simultaneously optimized imbalance compensation is formed by such an embodiment of the imbalance compensation element or such a method for the production of an imbalance compensation on a pump. 

1. An imbalance compensation element for fixing on one end of a motor- or pump-shaft, comprising: an inner circumferential surface coaxial to a central axis, the surface having an inside diameter corresponding essentially to an outside diameter of the shaft, wherein the inner circumferential surface has one or more flexible spring arms in a first section, wherein the one or more spring arms are disposed so that when in an installed state, the spring arms produce a frictional connection to the shaft in at least a circumferential direction.
 2. An imbalance compensation element according to claim 1, wherein said spring arms are embodied as ring segments extending in an axial direction.
 3. An imbalance compensation element according to claim 1, wherein said inner circumferential surface features a second section having grooves running in an axial direction.
 4. An imbalance compensation element according to claim 1, further comprising a closed outer circumferential surface, wherein over one or more first defined angular areas the closed outer circumferential surface is connected to said inner circumferential surface with a connection that is essentially completely filled with material, and wherein in one or more second defined angular areas, the closed outer circumferential surface is connected to the inner circumferential surface by one or more individual bridges.
 5. An imbalance compensation element according to claim 1, wherein the imbalance compensation element comprises one piece made by an injection molding process.
 6. An air injection reactor pump for combustion engines drivable by an electric motor having a drive shaft, wherein the pump comprises at least one impeller arranged on a drive shaft of the electric motor, and wherein when the pump is disposed for driving by the electric motor, one end of the drive shaft projects beyond the impeller in a direction facing away from the electric motor so that an imbalance compensation element according to claim 1 can be fixed on the one end of the shaft.
 7. A pump according to claim 6, further comprising a connection piece of said pump, coaxial to said drive shaft.
 8. A pump according to claim 6, wherein said imbalance compensation element is fixed on said drive shaft by means of an anaerobic adhesive.
 9. A pump according to claim 6, wherein said imbalance compensation element further comprises an axial outer surface, said pump impeller comprises a hub having a corresponding surface, and the axial outer surface of the imbalance compensation element and the corresponding surface of the hub correspond in their shape.
 10. A method for balancing an electric pump comprising the steps of: (a) providing a pump connected to an electric motor; (b) starting the electric motor; (c) measuring an oscillation acceleration to determine acceleration amplitudes in the axial and/or radial directions together with measuring an oscillation angular position to determine a balance angle and a balance class; and (d) placing a classified imbalance compensation element according to claim 1 in accordance with the determined balance angle and balance class.
 11. A method for balancing electric pumps according to claim 10, wherein said motor further comprises a drive shaft and said step (c) further comprises using a light barrier as well as a reflecting disk connected to the drive shaft with a positive engagement to measure said oscillation angular position.
 12. A method for balancing electric pumps according to claim 10, further comprising the use of a triax sensor is to measure said oscillation acceleration.
 13. Method for balancing electric pumps according to claim 10, wherein said measurements are carried out at an operating speed of the fully assembled pump.
 14. Method for balancing electric pumps according to claim 10, wherein said measurements are carried out at one or more mounts of said pump to a combustion engine or to a vehicle.
 15. Method for balancing electric pumps according to claim 10, wherein if said oscillation angular positions of said axial and radial acceleration amplitudes are not equal, said balance angle and said balance class are calculated by weighting the acceleration amplitudes taking into consideration the oscillation angular positions.
 16. Method for balancing electric pumps according to claim 10, further comprising a step of fixing said imbalance compensation element in a recess of an angular degree disk at a zero position; step (c) further comprises ascertaining the balance angle to the zero position; and step (d) further comprises turning said imbalance compensation element before fixing said element. 